Process for separating molybdenite from copper sulfide concentrates



United States Patent [72] Inventors Arthur W. Last Salt Lake City and George L. Fraser, Magnn, Utah [2|] Appl. No. 697,255 [22] Filed Dec. 11, 1967 [45] Patented Nov. 10, 1970 [73] Assignee Kennecott Copper Corporation New York, New York a corporation of New York [54] PROCESS FOR SEPARATING MOLYBDENITE FROM COPPER SULFIDE CONCENTRATES 7 Claims, 1 Drawing Fig,

[52] U.S.Cl. 209/3, 209/ l 1, 209/167 [5 1] Int. Cl B03b 1/00 [50] Field ofSearch.. 209/3, I I, 166, 167

AQUEOUS ULP OF COPPER SULFIDE-MOLYBDENITE CLEANER CONCENTRATE [56] References Cited UNITED STATES PATENTS Re. 22,1 17 6/1942 .lanney 209/3 2,559,104 7/1951 Arbiter.... 209/167 3,102,854 9/1963 Atwood 209/1 1X 3,137,649 6/1964 De Benedictis 209/I67X Primary Examiner- Frank W. Lutter Assistant Examiner-Robert HaIpr Attorney-John L. Sniado. Mallinckrodt & Mallinckrodt. P. H. Mallinckrodt, Philip A. Mallinckrodt and David V- Trash OBTAINED BY USE OF XANTHATE AS COLLEC OR REAGENT THICKENER I DISCARD EXCESS WATER AQUEOUS PULP 50-60% SOLIDS SODIUM HYPOC HLORITE STEAMER TEMP. AT OR NEAR BOILING 30 MIN.

DILUTION WATER CONDITIONED PULP -DEPRESSANT' 0.7a lbs/ion CELI- -BURNER OIL (COLLECTOR REAGEN (7 MIN.) 0J6 h/ton n FROTH CONCENTRATE (M05 CLEANER FLOTATION STAGE DEPRESSANT LI lb, ten

CELL METHYLAMYL I ALCOHOL (FROTHER) AS H ao REQU RED TAILING TIME MIN: 3 3 3,5 4.5

FINAL MOS; CONCENTRATE CLEAFER TAILINGS CRUDE SODIUM THIOPHOSFHATE AS DESCRIBED IN US. PATENT NO. 2,492,936 REAGENT CONSUMPTION IS GWEN IN POUNDS OF CONTAINED P 5 PER TON OF PROCESS FEED SOLIDS,

Paten td Nov. 10, 1970 I 7 3,539,002

I AQUEOUS PULP 'OF COPPER SULFIDE-MOLYBDENITE CLEANER CONCENTRATE OBTAINED BY USE OF xANTHA E As COLLECTOR REAGENT DISCARD EXCESS WATER AQUEOUS PULP TEMP. AT OR NEAR BOILING 30 MIN.

L COOLER DILUTION WATER CONDITIONED PULP DEPREssANT' 0.78 Ibs./Ion FLOTATION CELL R-BURNER OIL (COLLECTOR REAGENT) 7 MIN.) O.I6'lb./I0n

*METHYLAM.YL

ALCOHOL(FROTHER)AS pH a0 E I REQUIRED FR0TII CONCENTRATE I M082) TAII ING CLEANER FLOTATION CELL sTAGE DEPREGSANT TIME 0 Ib./I0n m I 0.2 3 2 0.02 3 3 0.07 3.5 4 0.07 4.5

FINAL CLEANER TAILINGS Mos CONCENTRATE CRUDE SODIUM THIOPHOSPHATE AS DESCRIBED IN US. PATENT NO. 2,492,936

REAGENT CONSUMPTION IS GIVEN IN POUNDS OF CONTAINED P 8 PER TON OF PROCESS FEED SOLIDS.

INVENTOR. ARTHUR W. LAST GEORGE L. FRASER W 2? I M W ATTORNEYS 1 PROCESS FOR SEPARATING MOLYBDENITE FROM COPPER SULFIDE CONCENTRATES BACKGROUND OF INVENTION 1. Field of the Invention I Y The invention relates to the art of froth flotation. It is particularly concerned with conditioning flotation concentrates of copper sulfide minerals containing relatively small amounts of molybdenite prior to subjecting the concentrates to differential flotation for the recovery of molybdenite mineral.

2. Description of the Prior Art Froth flotation involves the fine grinding of vmixtures of different minerals or of minerals'and gangue materials and subjecting them, in the form of an aqueous suspension or pulp, to agitation and aeration in the presence of chemical reagents which produce froth. Conditions are controlled to cause particles of one or more of the component materials to cling to the bubbles of the froth and rise therewith away from the body of pulp. When finely ground copper ores are subjected totlotation, there is typically recovered a concentrate including copper sulfide, iron sulfide and molybdenite. Additional processing is required to recover the individual constituents from these concentrates.

Various flotation processes have been previously developed and widely used industrially for separating molybdenite minerals from copper sulfide-molybdenite concentrates.-

chlorates, and the permanganates of the alkali and alkaline earth metals to the extent they are soluble in the alkaline pulp or suspension.

The quantity of oxidant employed is highly variable and depends in part upon the oxidizing power of the particular oxidant selected for use. An effective amount of the oxidant is all that is required. By "effective amount is meant an amount These processes are concerned with-either floating the molyb- 'The copper) producing industry has'long sought less costly and more efficientprocesses for separating molybdenite from copper sulfide flotation concentrates. Despite the cost of heating large volumes of flotation pulp, processes based upon steaming (heating) as a means of removing copper flotation.

circuit reagents and modifyingmineral. surfaces for reflotation have been favored and have continued to be employed in at least certain stages of an overall flotation procedure involving both, roughing and cleaning stages.

7 SUMMARY OFTHEINVENTI'ONI In accordance with the present, invention the. prior art steaming process is significantly, improved, fromthe standpoint of recoveryr-and overall costefficiency, by. introducing an oxidizing agent into the :pulp during the, heating stage.

Thus, instead of substitutingthe use of an oxidizing agent in a conditioning step for the customary conditioning byheating, we have found that results.superior tothoseobtained, by either heating or oxidizing are achieved by combining the two. Overall efficiency is.enhanced and economic returnsare increased by the practice ofthis invention.

Any oxidizing agent that functions as anoxidant for the organic collectorunder the conditions of the treatment maybe employed. Thus, any of the oxidants suitable for use under ambient conditions,such as those taught by the'aforesaid US. Pat. 2,559,104, maybe used in accordancevwiththe instant invention. Some oxidizingagents, e.g., the. dichromates, are.

more effective underacid'conditions while othersare more effective under basic conditions. Present commercial practices employ alkaline flotation conditions, so thoseoxidizing agents which are effective oxidants under alkaline conditions are of most immediateinterest. Suitable oxidantsof. this .type are readily determinable by those skilled in-the art, butinclude, by way i of example, the peroxides, the hypochlorites, f the sufficient to result in significantly more effective treatment of theconcentrate that would result from the application of heat alone. Skilled operators can readily determine the amounts of oxidizing agent required by observing the characteristics of the treated concentrate when it is fed to a differential flotation circuit. Inadequately treated concentrate carries undesirable amounts of frother into the flotation machine. The presenceof this frother is immediately apparent to the operator. Amounts of oxidizing agent less than the amounts employed at ambient temperature in accordance with the'prior art are effective in the practice of this invention. The upper limit to the quantity of oxidizing agent present is generally established by economic rather than process considerations. When sodium hypochlorite is the oxidizing agent employed, the amount used typically ranges from about 1 to about 10 pounds per ton of the solids fed to the process. Other oxidizing agents are used in amounts sufiicient to provide oxidizing power equivalent to between about 1 and about 10 pounds of sodium hypochlorite on the aforestated basis.

According to this invention, the concentrate is supplied to a treatment vessel in the-form of an aqueous suspension or pulp. An effective amount of oxidizing agent is supplied to the pulp. The pulp is then subjected to heating for sufficient duration to effect the treatment. The temperature of the pulp is raised to substantiallyabove ambient, i.e., above the equilibrium temperature of the concentrate due to its being processed under ambient conditions. Although heating to lesser degrees is beneficial, the pulp is ideally heated to at least approximately its normal boiling point. At these temperatures, treatment times as low as 5. minutesare often sufficient. In commercial practice, somewhat longer treatment times, e.g., about 15 to about 30 minutes, rarely more than l hour, are preferred. The temperature of the treatmentmay be raised to above the normal boiling point: of the pulp, if desired, by employing elevated pressure conditions.

According to the-most preferred embodiments of the invention, the treatment is conductedunder conditions of high lime alkalinity. That is, the pH of the pulp is raised to above about 11, ideally between about 1 l to about 12.2 by the addition of lime prior to or during the treatment. It is also desirable to adjust the water content of the pulp to provide about 50 to about 60 percent by weight. solids in-the pulp during the claimed treatment.

THE. DRAWING The flowsheet in the accompanying drawing illustrates a preferred embodiment of the process applied to a concentrate containing both molybdenite and copper sulfide minerals. The procedures indicated represent the best mode presently contemplatcd of carrying-out the invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT As illustrated, feed concentrate, in'theform of an aqueous pulp, ispreferably firstc'onditioned withlime to raise thepH above 11, rag. to 12.2. It is then partially dewatered by thickening in customary manner to produce an -aqueous pulp containingSO to 60 percent solids. The oxidizing agent, which is-preferably sodium-hypochlorite because of its availability, low cost, and excellent performance, is added on the basis of 4.1 pounds per ton of solidsfed to the process. The resulting.

pulp isthen subjected to the usual steaming treatment, whereinlive steamis injected thereinto to raise it to or near its boiling point. The pulp is held at elevated temperature for an appropriate duration, typically about 30 minutes, after which it is cooled and diluted with water. Sufticientwater is added to effect a pulp density suitable for the subsequent reflotation step by which molybdenite is floated away from the copper and iron sulfides with which it is mixed.

Flotation of the molybdenite is carried out in customary manner, with the usual collector and frother reagents specific to molybdenite. Nokes reagent can be used, as indicated, as a supplementary depressant for the copper sulfide minerals. In the illustrated instance, the rougher flotation stage was followed by four cleaner stages to produce the final MoS- concentrate. The number of stages employed in any given instance will, of course, depend upon the particular ore concerned. Small additions of the Nokes reagent are advantageously made in the several cleaning stages to assist the cleaning operation.

it has been found that not only are the amounts of chemical reagents and processing stages reduced over prior practices, but the economic recovery of molybdenite is enhanced in terms of grade of the concentrate recovered, percent MoS recovered, or both.

Example I As an example of the effectiveness of the present process, the following comparative tests are given:

TEST NO. 1

This test was carried out in standard laboratory equipment utilizing 1,530 grams of a copper sulfide-molybdenite flotation concentrate analyzing as follows:

M03 0.43% Cu, 26.60%

and conditioned and processed as indicated in the flowsheet. The rougher concentrate contained 98.98 percent of the MoS present in the initial feed. Three stages of cleaning yielded a concentrate assaying 94.5 percent MoS with a recovery of 85.55 percent of the M05 present in the initial feed; four stages yielded a concentrate assaying 97.6 percent Mos: with a recovery of 72.52 percent of the MoS present in the initial feed.

A table of metallurgical results follows:

Molybdenite Copper Weight, Percent Percent percent Percent dist. Percent dist.

Telling (sink) 88. 40 0.005 1. 02 26. 5 88. 17 N0. 1 Cl. tailing 9.30 0. 18 3. 88 28. 6 10.00 No. 2 Cl. tailing.. 1. 62 1.03 3.88 27.0 1. 64 N0. 3 Cl. tailing 0. 12. 2 5.67 21. 8 0. 16 N0. 4 Cl. tailing 0.07 80.1 13. 03 6. 50 0. 02 MOS: Cl. cone 0. 32 97. 6 72. 52 0.70 0. 01

Cale. feed 100. 00 0. 43 100. 00 26. 6 100. 00

TEST NO. 2

This test was made on another batch (1,518 grams) of the copper sulfide-molybdenite concentrate of test no. 1, but followed the so-called Morenci" process of the aforementioned prior art U.S. Pat. No. 2,559,104. Thus, an oxidizing agent was employed instead of heating to modify pulp and mineral conditions.

Based on the solids in the pulp, the initial feed was treated, with 4.4 pounds/ton of lime to raise the pH to 12.2 and was thickened as in the first test. It was then conditioned with 6.2 pounds/ton of sulfuric acid, 32.7 pounds/ton of sodium hypochlorite, 26.7 pounds/ton of sodium ferrocyanide, and 9.36 pounds/ton of burner oil and subjected to rougher flotation for 7 minutes at pH 7.6. The MoS concentrate from this stage was then cleaned twice, 2.3 pounds/ton sodium hypochlorite and 4.4 pounds/ton sodium ferrocyanide being used for the first cleaning stage (7 minutes), and 0.4 pounds/ton of sodium cyanide for the second cleaning stage (3 minutes).

The metallurgical results were as follows:

Molybdenite Copper Weight, Percent Percent percent Percent dlst. Percent dist.

'Iailing (Sink) 53. 15 0. 022 2. 19 22. 0 45. 44 No. 1 Cl. talling 40. 36 0.10 7 55 31.3 47. 79 No. 2 Cl. tailing. 2.07 0.28 1. 08 30. 9 2. 42 MoSzCl. cone. 4. 42 10. 8 89. 18 26. 0 4. 35

C810. fecd 100.00 0. 54 100.00 26. 4 100.00

Thus, it can be seen that the process of the invention yielded marketable grade concentrates with three stages of cleaning, while the prior art process produced concentrates of only 10.8 percent grade. in all, reagent consumption was considerably reduced by the process of the invention.

EXAMPLE II This example compares results from several laboratory flotation tests. Tests A and B correspond to present commercial practices. Tests C, D, E, and F are illustrative of the present invention. In each of the tests, an aqueous pulp of copper sulfide-molybdenite cleaner concentrate, collected by a xanthate collector in the presence of pine oil, was mixed with lime on the basis of about 6.5 pounds/ton of solids to adjust the pH of the suspension to about 12.2. The pulp was thickened to about 50--55 percent solids by the removal of excess water. The thickened concentrate was treated for 30 minutes by boiling, contact by an oxidant, or both, as indicated in the table. In test C, D, E and F, the oxidant was added just before the pulp reached boiling temperature. The conditioned pulp was cooled and diluted to suitable pulp density for feed to the molybdenite flotation machines. The following table reports metallurgical values.

Test

A B C D E F Steam No Yes Yes Yes Yes Yes Oxidont NaOCl No NaOCl KMnOi K0103 H 02 Taillng (sink):

Weight, percent 45. 87 93. 46 95. 07 96. 65 96. 23 95. 76 MoSz, percent... 07 07 07 09 06 65 Cu, percent 8.21 18. 1 17. 1 19. 3 17.5 18. 1 Distr. M082, percent. 5. 76 11. 61 10. 75 13. 96 11. 07 8. 94 Distr. Cu, percent. 16. 90 91. D6 95. 96 97. 3!) 96.31 96 69 MoSz rougher eoncentr Weight, percent- 54. 13 6. 54 4. 93 3. 35 3. 77 4. 24 M08 percent- .97 7. 61 11.2 16. 12. 3 11. Cu, percent... 28. 0 22. 6 21. 2 14. 9 17. 1 18. 4 Dlstl'. MOSz, percent 94. 24 88. 39 89. 25 86. 04 88. 93 01. 06 Distr. Cu, percent 80.10 8. 04 6. 04 2.61 3. 69 4. 31 Calculated feed:

M052, percent .56 56 .63 .62 52 .54 u, percent 18. D 18. 4 17. 3 19. 2 17. 5 18. 1 Reagents, 1b./ton feed solids:

Limo 6. 5 6. 5 6.5 6. 5 (i. 5 6. 5 4. 4. 2 0. 0 2. 3 2. 0 Burner oil .2 .2 .2 .2 2 .2

Methyl amyl alcohol added as required to maintain froth copper sulfides by a subsequent flotation step, the improvement which comprises introducing into an aqueous suspension of said flotation concentrates at atmospheric pressure an oxidizing agent, other than air; and subsequently heating at atmospheric pressure and under alkaline conditions said aque- I ous suspension with said oxidizing agent therein at a temperai ture and for a period of time sufficient to oxidize said collector l reagent. 2. The improvement of claim 1 wherein the aqueous suspension is heated to a temperature at least approximately its boiling point.

3. The improvement of claim 1 wherein the oxidizing agent is present in an amount to provide oxidizing power equivalent to between about 1 and about 10 pounds of sodium hypochlorite per ton of process feed solids.

4. The process of claim 1 wherein the solids content of the aqueous pulp is adjusted, to about 50 to about 60 percent solids before the pulp is subjected to heating.

5. The improvement of claim 1 wherein the heating is conducted under conditions of high lime alkalinity.

6. The improvement of claim 5 wherein the pH of the aqueous suspension is adjusted to between about 1 l and about 1 2.2 during heating and the oxidizing agent employed is an oxidant for the flotation reagent under alkaline conditions.

7. The improvement of claim 6 wherein the oxidant is selected from the group consisting of the inorganic peroxides, hypochlorites, chlorates and permanganates which are soluble in the alkaline aqueous suspension. 

